1. Field of the Invention
This invention relates to housings for systems, and more particularly is concerned with protective housings for a system that protect the system from its environment and that protect the environment from the system, wherein the protective housings include a first or inner housing for holding the system and a second or outer housing surrounding the first or inner housing and the system held therein, and wherein the first or inner housing is compatible with the needs of the system and the second or outer housing has sufficient properties to provide protection against damage caused by outside agencies found in the environment of use of the system.
2. Description of the Prior Art
Generally, a housing around a system protects the system from its environment. For example, a housing may provide protection of a system contained or held in the housing by blocking one or more outside agencies, such as objects, sunlight, chemicals, temperature, electrical interference, and fire, found outside the system in the environment of use of the system, from coming into contact or interfering with the system, thereby protecting the system from being damaged or compromised by one or more of such outside agencies. Further, generally, a housing provides structure or support to the system, and must meet the needs called for by the system.
In some instances, a housing may provide all of the structure and protection required, being compatible with the needs of the system while at the same time having sufficient properties to fulfill the protection requirements demanded by the environment in which the system is used.
However, there are other instances where the housing meets the needs of the system, such as the structure and support requirements of the system, but does not meet the protection requirements demanded by the environment in which the system is used. For instance, in many aircraft, apparatuses for filtering and/or purifying and/or conditioning water are provided in galleys for providing potable drinking water, with each such apparatus comprising a housing (e.g., a pressure vessel) and filtering medium held within the housing, that is, the pressure vessel. The pressure vessel in many cases is made from polypropylene. While the polypropylene pressure vessel has sufficient strength to handle the pressure created within the pressure vessel and polypropylene is compatible with the production of potable water, polypropylene is flammable. Accordingly, while the housing, that is, the polypropylene pressure vessel, meets the needs of the water filtering/purifying/conditioning system to enable the production of potable water, the polypropylene pressure vessel does not protect the water filtering/purifying/conditioning system against catching on fire if a fire broke out in the galley. For example, polymers that meet the anti-flammability requirements desired for a water filtering/purifying/conditioning pressure vessel used in the galley of an airplane are not strong enough to handle the pressure created within the pressure vessel and/or are not compatible with producing potable drinking water or may be excessively expensive, heavy or sub-optimal in other attributes.
Therefore, a problem exists where a housing meets the needs of a system, but does not meet the protection requirements demanded by the environment in which the system is used.